The present invention refers to the field of shape-memory actuators of the type comprising at least a shape-memory element, which can change its shape upon variation of its temperature beyond a transition value, and means for supplying an electric current through the shape-memory element in order to cause a variation of its temperature.
Shape-memory elements have been known and used for a long time in several technical fields. They exploit the property of some metal alloys, which are able to undergo a change in state when temperature varies beyond a transition value. The Applicant is owner of several patents and patent applications concerning applications of shape-memory actuators in many fields, for instance in the automotive field, for controlling locks of motor vehicle doors, distributing devices in air conditioning systems for motor vehicles, adjustment devices for rear-view mirrors, etc. The Applicant has proposed in particular shape-memory cable actuators (either flexible-cable or stiff-cable actuators), i.e. independent devices that can be used in several fields for controlling any mobile member (see for instance WO 03/003137 A1).
The advantage of shape-memory actuators consists in that they have a relatively simple and cheap structure, with small size and low energy consumption. Studies and tests made by the Applicant in view of a wide application of shape-memory actuators, for instance for controlling a series of operating members in a motor vehicle, have pointed out the need and advantage of developing control systems and methods enabling a further improvement of the efficiency and advantages of said actuators.